Drip irrigation emitters may be formed from several parts, such as an outer housing formed e.g. from two members. Drip irrigation emitters typically have an inlet through which water flowing in a pipe can enter the emitter and an outlet through which water that entered the emitter can exit to the outside environment. The emitter diverts a relatively small portion of water flowing in the pipe and discharges the diverted water to irrigate plants in a neighborhood of the location of the emitter.
To control the rate at which water is discharged by the emitter, the emitter typically includes a flow restricting path that functions as a pressure reduction channel and is normally referred to as a “labyrinth channel” or “labyrinth”. Through the flow restricting path water that enters the emitter must flow to reach the emitter outlet. The flow restricting path is a high resistance flow channel along which pressure of water flowing through the emitter drops relatively rapidly with distance along the path. The pressure drop is from a relatively high water pressure at the emitter inlet, to a relatively low discharge pressure, generally a gauge pressure equal to about zero, substantially at or near the emitter outlet.
Drip emitters may also include a resiliently flexible part often referred to as a membrane or diaphragm that may operate e.g. to control the rate of liquid flowing out of the emitter, so that it is substantially independent of inlet pressure for a range of pressures typically encountered in irrigation applications which may be equal to a flow rate between about 0.4 and 12 liters per hour (1/h). The membrane is usually located between the inlet and the outlet and may contain at one side water that enters the emitter inlet to pass through the labyrinth and at the other side water that already passed through the labyrinth and reached a pressure regulating chamber that in some cases is located adjacent the emitter outlet. A pressure regulating chamber located adjacent an emitter outlet, typically has a wider cross section than the labyrinth emptying into it, in order to provide improved pressure regulating performance for the emitter. The membrane in response to increase in pressure of the entering water, may flex into the pressure regulating chamber to restrict the flow of water exiting the outlet and by that act to control the rate of liquid flowing out of the emitter.
U.S. Pat. No. 6,250,571 shows a drip emitter that is adapted to be bonded to an inner surface of a water supply tube. The emitter has elongated body and cover members and a membrane that is located therebetween. The cover is integrally formed with four pins that pass through holes formed in the body member and project out of the holes to bond to the inner surface of the water supply tube. The pins are located at opposing longitudinal sides of the membrane and by the bonding to the water supply tube secure the membrane between the body and cover members.
U.S. Pat. No. 4,060,200 shows another drip emitter which is formed from first and second components with a strip interposed therebetween. The first component is formed with pins that extend through apertures in the strip into appropriate apertures in the second component. The two components brought together become press fastened to each other with the strip forming a dividing wall which contributes to defining the flow path in both components.